Re: [FR] RefTex support for zref-xr

[Gustavo Barros]

Hi Arash,

On Fri, 10 Dec 2021 at 23:14, Arash Esbati <arash@gnu.org> wrote:

> Now we are 2 ;-)

I'm thinking here, and since we are trying some ideas out, I'd like to 
take a step back, and make an argument.  Perhaps you'll disagree, but 
please bear with me.

(I'm reordering your comments to highlight some connections).

> This is the `Naked label' in RefTeX.  Our labels are not bound to any
> sections/environments, and for the others, RefTeX takes \label (which 
> is
> hard-coded, AFAICT).

> The issue is that \zlabel doesn't get a prefix like 'fig:' in the 
> first
> place [...].

I was unsure about this in the last message, but I thought it through 
and tested things out, and this limitation is actually a consequence of 
using `(reftex-add-label-environments '(("\\zlabel{*}" ?z nil nil 
nil))', because, if we use `(reftex-add-label-environments 
'(("\\zlabel{*}" nil nil nil nil)))', we do get prefixes and context 
derived labels, as 'fig:', 'sec:section-1' etc. (The prompt does say 
"Naked label", but the content is just the same as for regular 
`\label's).

So we actually loose functionality both in label querying for setting 
references and in label setting itself.  In the first case we loose the 
capacity to narrow by type of label.  In the second we loose all prefix 
and context derived labels by RefTeX.

It is quite a lot to forgo, I'd say. In my last message I had understood 
the first, but I'm adding the second to the discussion.

> Thanks, I think this can a be compromise for all users: Serious 
> \zlabel
> users will to use it exclusive as a replacement for \label, and casual
> users will have two label circles.

> [...] adding 'z:' should be easy with RefTeX (didn't test it though).

I'm no longer sure the `("\\zlabel{*}" ?z nil nil nil)' is the best 
approach, for the reasons mentioned above.  If it turns out to be the 
only one, then there's no choice.  But *if* the "z:" prefix to the 
labels is indeed feasible, I think using it with `("\\zlabel{*}" nil nil 
nil nil)' would be a superior alternative.

It is (much) less complex, we'd get full support from RefTeX, including 
narrowing by type, label prefixes, and context derived labels.  And it 
does avoid the potential clashes of the two separate sets of labels on 
the LaTeX side: with the "z:" prefix, they don't mix. Hence, RefTeX does 
not confuse them, no duplicate problems. And users do not confuse them 
either, since they have the prefix hint.

Admittedly, your `LaTeX-zref-replace-label' would mitigate the 
limitations of `("\\zlabel{*}" ?z nil nil nil)', but we'd still have two 
ways of setting the zlabel with radically different behaviors.

So, for now, I'm refraining from entering into the details of 
implementation in this area.  Because, in the chance I was able to 
convince you, those might be superfluous.  But, if you do disagree, then 
I'll come back and comment on them with pleasure.

Still, a thank you for `LaTeX-zref-reftex-quick-id-key', is due. It is 
great. :-)

> I have another idea: For serious users, we can replace \label with
> \zlabel.  For sectionning commands, we need to add function to
> `LaTeX-section-hook' which looks back for a \label and adds a 'z' to 
> it.
> For environments, the same logic would apply, but
> `LaTeX-after-insert-env-hook' is not the right place since it is run 
> to
> early.  I have to think about it.  See attached a new version with the
> first idea implemented.  Maybe you want to give it a roll. You have to
> set `LaTeX-zref-replace-label' before it works.

This is to some extend a separate issue, and is good stuff.  It was 
actually in my list to discuss later on, so I'm glad you brought it up.

Besides the above mention that this is much welcome, I have two further 
comments.  One about some `zref's limits, with some implications to 
label setting, and the other about the technical side of getting 
`\zlabel's out of `reftex-label'.

About the first, even for users who want to use `zref' as their main 
reference system, it may be quite hard to use it exclusively because 
some places which handle labeling specially, do not offer support for 
`zlabel'.  There are two conspicuous general cases for this: places 
where `\label' cannot be set directly and must be passed as an argument 
to a command or environment; places where `\label' has special support.

One relevant example of this are `amsmath' display environments: 
https://tex.stackexchange.com/a/402297.  There are work-arounds to get 
things working for `zref': https://tex.stackexchange.com/a/618438, but 
they rely on making `\label' set a `\zlabel' for us.  Therefore, within 
them, `\label' is all AUCTeX/RefTeX will ever see when parsing the 
document.

All this to say some exception handling may be needed when replacing 
`\label's with `\zlabel's.  However, even when it's not possible to do 
so, a way to get `\zlabel's from `reftex-label' (called directly, or 
indirectly by some hook), as you are proposing, is still much welcome. 
And I concur it should be "opt-in", as you made it.

On the technical side, I have some stuff to do the same job here, using 
`reftex-format-label-function', which may interest you.  It's a little 
crude, but only the basic idea is relevant anyway:

#+begin_src elisp
(defvar gb/LaTeX-prefer-zlabel nil
 "If non-nil prefer '\\zlabel' over '\\label' when zref-user is 
 loaded.")

(defun gb/zref-user-reftex-format-label-function (label default)
 (if (and gb/LaTeX-prefer-zlabel
          (string= default "\\label{%s}")
          ;; 'amsmath' display environments do not support 'zlabel'.
          (not (and (TeX-match-style "amsmath")
                    (member
                     (LaTeX-current-environment)
                     '("equation"
                       "equation*"
                       "align"
                       "align*"
                       "alignat"
                       "alignat*"
                       "flalign"
                       "flalign*"
                       "xalignat"
                       "xalignat*"
                       "gather"
                       "gather*"
                       "multline"
                       "multline*")))))
     (format "\\zlabel{%s}" label)
   (format default label)))

(setq-local reftex-format-label-function
           'gb/zref-user-reftex-format-label-function)
#+end_src

I may be missing something you are trying to do with 
`LaTeX-zref-replace-label-section' and 
`LaTeX-zref-replace-label-environment' but, as far as I grasp, it is 
pretty much the same job, in which case `reftex-format-label-function' 
may be an interesting alternative "hook".  I'm not sure if "better", 
just bringing it in for your consideration.


Thank you very much once again.

And once you let me know what you think about the 
`reftex-add-label-environments' issue, I'll be glad to provide further 
comments appropriate to the ensuing "branching".

Best regards,
Gustavo.